At the risk of stepping into the line of fire - let me say that almost all accessibility depends on effort from BOTH the content and user agent side.
In fact there are essentially no websites that are accessible to people who are blind directly. They all depend on the user having a user agent that can voice (or braille) the contents. And the screen readers depend on the information being machine readable so that the screen readers can access it.
In the case in point, Phil was pointing out the the information in question was already all machine readable.
Now - is that good enough?
I would argue that it SHOULD be - BUT IT WOULD BE good enough ONLY IF user agents were all developed appropriately and had the right features on them. Those that wanted to know when pages were external would set that feature on their browser and an icon (or verbal cue if people preferred) would appear next to each external link so it was visible to those who wanted that information -- and Screen readers would announce them. And those that didn’t want that information would not
BUT IF THEY DO NOT - If user agents are not available that will expose this information to the user -- then the author should not rely on this to make the page accessible. They should do it explicitly so that everyone can use the page.
And YES - authors should pressure user agent developers to include these features so that there is less for the author to do.
Gregg
(this is a personal comment and does not necessarily reflect the opinion of the WCAG working group, WAI, W3C, the UN, or the United Federation of Planets)
-----------------------
Gregg Vanderheiden Ph.D.
Director Trace R&D Center
Professor Industrial & Systems Engineering
and Biomedical Engineering
University of Wisconsin-Madison
>